Verizon is moving insanely quickly with the growth of their 4G LTE network, so it may make you wonder when the carrier will flip the switch to shut down its 3G network and have its users rely solely on its 4G LTE. ItÃ­s going to happen at some point, obviously, but Verizon says that itÃ­s going to shut down its 2G and 3G networks by 2021.